PURPOSE: To prevent the initialization processing of a system from being erroneously performed.

CONSTITUTION: An initialization switch 5 is formed with the one of non-lock type, and a CPU 1 reads in the state of the initialization switch 5 only when a power source is applied, and when the power source is applied while operating the initialization switch 5. the fact that the initialization switch 5 is turned on is detected, and system data in a RAM is returned to an initial value. When only the power source is applied in the initialization processing, the CPU 1 detects the fact that the initialization switch 5 is turned off when a power source switch 6 is turned on, and starts an ordinary operation without changing the system data. As a result, since the initialization switch 5 is formed with the one of non-lock type and an operating state is not stored, and also, the CPU 1 identifies the state of the initialization switch 5 only at a moment when the power source switch 6 is turned on, it is possible to prevent the initialization processing from being started up erroneously by the mis-operation of the initialization switch 5 when the power source is applied or the system is operated.